1. Field of the Invention
This invention relates to the field of radiography and more specifically to lead and lead oxide screens used to intensify images produced using industrial radiography. Still more particularly, this invention relates to an improved screens employing lead foils or lead oxide formulations applied to film supports and used with photographic industrial X-ray elements.
2. Discussion of the Prior Art
Industrial radiography is a system used to determine the quality of welds castings and metal or composite materials under stress or strain, such as the girders of bridges or the fuselages or wings of aircraft, for example. This system is also used to determine defects within smaller items such as various parts that cannot be visually inspected. Conventionally, a special photographic film is placed near the device to be radiographed, and X-radiation is applied thereto. Even though photographic, radiographic elements are not particularly sensitive to X-rays, large doses of these X-rays can be applied since they will not harm the items being examined in this manner. The use of lead and lead oxide containing screens and foils in conjunction with industrial, radiographic photographic elements to produce quality images, is well-known. These screens are conventionally comprised of a lead coating on paper or cardboard. These screens serve to intensify the radiographic image somewhat, and produce a sharper image by absorbing scattered X-rays, and find great utility within the described system. Flexibility is important within this system since it is sometimes necessary to wrap the film and screen around the item to be radiographed in order to obtain an image of the entire interior thereof. Although these screens are conventional, there are drawbacks to the use thereof since both the paper or cardboard support are not fully flexible and tend to kink, causing irregular absorption of radiation at this kink. Also, these supports tend to absorb moisture and this can adversely affect the photographic emulsion associated under vacuum there-with. Also, these supports add curl to the combination making handling very difficult. Also, paper can absorb X-radiation and thus interfere with the process of producing and X-ray image on the photo-graphic film.
It is also known to coat a layer comprising lead and lead oxide dispersed in a binder on various film supports. These elements have not met with wide spread acceptance since the problems of moisture absorption are still present and it is difficult and costly to apply lead in this manner to these supports.